Disposal of aqueous waste is a costly and bothersome problem. Many methods of disposal which are desirable from a cost standpoint are unacceptable from the standpoint of safety to the environment. The present invention is directed towards a process of disposing of waste materials, particularly organic or chemical aqueous waste, in a manner which is both cost efficient as well as safe to the environment.
It is not unusual for a very large amount of waste solution to require disposal. These waste materials are the by-products of various chemical processes, including the preparation or synthesis of chemical compounds and can be residual (not hazardous) or toxic or result in the formation of toxic by-products. The presence of these pollutants in the aqueous waste solutions prohibit their disposal in streams or other aquifers, and burial of these materials underground is of questionable safety. Likewise, disposal of odoriferous wastes may be difficult because of the pollution of the atmosphere.
The present invention contemplates the treatment of a wide variety of aqueous wastes. The combustible materials present as pollutants in the aqueous waste may consist of a dissolved or dissociated solid, i.e. a sugar or a salt, a solid material dispersed in the aqueous solution, i.e. starch, an organic compound, i.e. an alcohol or a glycol, or an inorganic substance, i.e. fumed silica. One example of a waste solution is brewery waste which not only includes ethyl alcohol, but also is extremely odoriferous because of the yeast, malt and alcohol contained in it.
In the past, disposal of aqueous wastes has been accomplished in a variety of ways. Disposal by dumping onto the land or into streams or other aquifers is no longer tolerated by our society. One alternative has been to treat the aqueous wastes in sewage treatment plants. Since many of these aqueous wastes contain toxic materials, the solutions require extensive pretreatments to remove the toxic pollutants before the solutions can be treated in a conventional sewage treatment plant. This method has suffered from a number of drawbacks. Primarily, such pretreatment is extremely expensive. Secondly, many sewage treatment facilities do not have sufficient capacity to carry out the necessary treatment on large quantities of toxic waste materials.
Non-aqueous wastes have been combined with the fuel fed to a kiln to effect combustion of the wastes, but the water content of the aqueous wastes renders this procedure inappropriate for disposal of aqueous waste. It has been attempted to dispose of such waste solutions by employing the solutions as the liquid component of a slurry being fed to a Portland cement kiln. The solid component of the slurry is comprised of cement raw materials, such as clay, sand, or stone. The solid and liquid components of the slurry are ground to form the finely ground slurry, which is then burned in the Portland cement kiln. Normally, clean water is employed as the liquid component of the slurry. By replacing the clean water normally used in the slurry with aqueous waste, the toxic materials and other combustible pollutants which are present in the waste solution are fed to the cement kiln where they are burned at a temperature sufficiently great to decompose the pollutants and toxic materials. This procedure, though desirable from a cost efficiency standpoint, has suffered from a major disadvantage. The waste solutions being treated often contain at least a portion of pollutants which are volatile at temperatures considerably less than the operating temperature of the kiln or the temperature at which the volatile pollutants are decomposed. When these volatile pollutants are present in the feed slurry entering the cement kiln, these volatile components can be vaporized by the effluent stream within the cement kiln before the feed reaches a point in the kiln where decomposition occurs. The effluent stream from the kiln can therefore contain vaporized pollutants which may constitute an explosive hazard in the duct work, fans, collector or the stack, and which are also in the effluent stream leaving the kiln to be expelled into the atmosphere. For this reason, the gaseous effluent from the cement kiln apparatus containing these pollutants has not met the approval of the regulatory agencies.